Thermoplastic polymers are often colored in the molten state by the addition of color concentrates. Color concentrates are highly loaded dispersed colorants in a carrier polymer. The carrier polymer being either the same chemistry, with higher melt flow characteristics as or compatible with the polymer to be colored. Color concentrates are generally used to ensure good dispersibility and incorporation of pigments and other additives. Use of color concentrates can also create a much cleaner environment for an end user who does not have to involve oneself with dusty colorants and other hard to handle materials.
There are several methods for adding a color concentrate to a thermoplastic polymer that is to be colored. However, the most common method utilized today involves the controlled metering of the color concentrate into the throat of a polymer extruder or injection molding machine using pellet feeders. In this application, the concentrate is supplied in a pellet form.
Color concentrates containing metal particles are known in the prior art. Such concentrates are utilized to impart a metallic look or effect to polymers. However, to date, the use of such concentrates has presented a variety of problems including poor incorporation or distribution of the metal within the polymer, low metal loading levels that fail to produce a meaningful metallic effect in the polymer being colored and the formation of knit lines, flow lines, diration lines and other molding marks upon use of the colored polymer. Moreover, such concentrates have commonly been made using a wax carrier, and waxes at higher concentrations are undesirable in many applications. The present invention affords a metal filled color concentrate that overcomes these deficiencies.